/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.trino.operator.scalar;

import com.google.common.collect.ImmutableList;
import io.trino.metadata.SqlScalarFunction;
import io.trino.spi.function.BoundSignature;
import io.trino.spi.function.FunctionMetadata;
import io.trino.spi.function.Signature;
import io.trino.spi.type.Type;
import io.trino.spi.type.TypeSignature;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;

import static io.trino.spi.function.InvocationConvention.InvocationArgumentConvention.NEVER_NULL;
import static io.trino.spi.function.InvocationConvention.InvocationReturnConvention.FAIL_ON_NULL;
import static io.trino.spi.function.OperatorType.CAST;

public class IdentityCast
        extends SqlScalarFunction
{
    public static final IdentityCast IDENTITY_CAST = new IdentityCast();

    private IdentityCast()
    {
        super(FunctionMetadata.operatorBuilder(CAST)
                .signature(Signature.builder()
                        .typeVariable("T")
                        .returnType(new TypeSignature("T"))
                        .argumentType(new TypeSignature("T"))
                        .build())
                .build());
    }

    @Override
    protected SpecializedSqlScalarFunction specialize(BoundSignature boundSignature)
    {
        Type type = boundSignature.getReturnType();
        MethodHandle identity = MethodHandles.identity(type.getJavaType());
        return new ChoicesSpecializedSqlScalarFunction(
                boundSignature,
                FAIL_ON_NULL,
                ImmutableList.of(NEVER_NULL),
                identity);
    }
}
